Human stem cells are totipotential, pluripotential or multipotential precursor cells capable of generating a variety of mature human cell lineages. Stem cells can be employed to repopulate many, if not all, tissues and restore physiologic and anatomic functionality. For example, cell populations containing stem cells have been used in transplants to restore partial or full hematopoietic function in patients who have undergone ablative therapy.
Recently, Hariri has reported the isolation of stem cells from mammalian placentas, and the characterization of those stem cells. See Hariri, U.S. Application Publication No. 2002/0123141 “Method of Collecting Placental Stem Cells,” Hariri, U.S. Application Publication No. 2002/0160510 “Renovation and Repopulation of Decellularized Tissues and Cadaveric Organs by Stem Cells,” Hariri, U.S. Application Publication No. 2003/0032179 “Post-partum Mammalian Placenta, Its Use and Placental Stem Cells Therefrom,” and Hariri, U.S. Application Publication No. 2003/0180269 “Embryonic-like Stem Cells Derived From Post-partum Mammalian Placenta, and Uses and Methods of Treatment Using Said Cells”.
Many different types of mammalian stem cells have been characterized. See, e.g., Caplan et al., U.S. Pat. No. 5,486,359 (human mesenchymal stem cells); Hu et al., WO 00/73421 (methods of isolation, cryopreservation, and therapeutic use of human amniotic epithelial cells); Boyse et al., U.S. Pat. No. 5,004,681 (fetal and neonatal hematopoietic stem and progenitor cells); Boyse et al., U.S. Pat. No. 5,192,553 (same); Beltrami et al., Cell 114(6):763-766 (2003) (cardiac stem cells); Forbes et al., J. Pathol. 197(4):510-518 (2002) (hepatic stem cells).
The success of transplantation of stem cells is significantly related to the numbers of engraftable cells administered. The number of engraftable cells in, for example, a unit of cord blood, and the amount of cord blood, that may be obtained from a single donor can vary by two orders of magnitude. See, e.g., Gluckman, Hematology, American Society of Hematology Education Program Book, 1-14 (1998). Therefore, a need exists for a method for improvement of the engraftment potential of units of cord blood, cord blood-derived nucleated cells, or other stem cells, especially prior to transplantation.